Urinary tract infections (UTI) caused by uropathogenic Escherichia coli (UPEC) result in 8 million outpatient visits (mostly by women) and over $1 billion in health care costs annually in the U.S. Recurrent UTI (rUTI) is a significant problem: >25% of women who suffer from an acute UTI experience a rUTI within 6 months. To address this problem, Project 2 is enrolling a cohort of women presenting with acute cystitis but no recent history of UTI. Bacterial isolates from the urine of these patients will be characterized in our mouse model in Project 1. We have detailed a pathogenic cycle within mice in which UPEC invade superficial umbrella cells that line the bladder and rapidly replicate to form a densely packed, biofilm-like intracellular bacterial community (IBC). Bacteria within an IBC are protected from both host innate immune defenses and many antibiotics, thus allowing one bacterium to clonally replicate to 10,000 or more bacteria within hours after infection. IBCs eventually disperse, with bacteria fluxing out of the cells and going on to repeat the IBC cycle within another epithelial cell or going on to form a quiescent intracellular reservoir (QIR). QIRs can persist for months and then later seed a rUTI. We will determine whether IBC and QIR formation is a general property of UPEC and whether prominent features of these cycles differ between bacteria causing different clinical UTI syndromes (asymptomatic bacteriuria, acute infection, or recurrent infection) and between different host genetic backgrounds. We have completed the genome sequence of cystitis strain UTI89 in Project 3 and will use this with additional sequence information to computationally search for candidate genetic determinants of pathogenesis and recurrence. These candidate genes will be analyzed in our murine model, in part by investigating the effects of mutations using advanced imaging methods, laser capture microdissection, functional genomics, and gfp fusions. Host responses will be characterized by immunohistology, flow cytometry, and cytology. Mass spectrometry will be used to profile qualitative and quantitative changes in both host and pathogen factors to identify those with pathophysiologic and prognostic significance. The combined expertise of the three projects in this SCOR will allow a coordinated effort to understand the epidemiology and basic pathogenic mechanisms of UTIs in women, allowing us to begin addressing clinical questions in the management of UTI.